1. Field of the Invention
The present invention relates to an information storage medium having an excellent oxidation resistance that can be quickly determined.
2. Description of the Related Art
Recording films in which information is recorded by forming pits using a semiconductor laser beam are known. For example, tellurium films are known as recording films having high sensitivity. However, tellurium recording films are susceptible to oxidation, and therefore their information write performance (a state wherein pits can be formed in the optical recording film) cannot be maintained for long periods of time.
Attempts have been made to slightly modify the tellurium film while retaining its advantageous characteristics. For example, a recording film containing tellurium and carbon is formed by depositing tellurium and carbon together, hereinafter referred to as a co-deposition Te/C film (W. Y. Lee et al, Proceedings of SPIE 382, 282 (1983)).
In addition, it is known that if a tellurium target is sputtered in an atmosphere of a hydrocarbon gas or mixture of a hydrocarbon gas and an inert gas, an optical recording film having a structure in which tellurium clusters are dispersed in a matrix containing carbon is obtained (U.S. Pat. No. 4,433,340). This is known as a Te/C film.
The co-deposition Te/C film, however, does not have excellent oxidation resistance. However, the recording film containing tellurium and carbon formed by the above sputtering is excellent in oxidation resistance. But, if the manufacturing method used to produce the film is not known, it is difficult to discriminate between these two films based on their appearances. For this reason, oxidation resistance of a film must be determined by performing an acceleration test to check the decrease in reflectance of the film under high temperature and humidity. This test is very time-consuming, taking as long as 1,000 hours or more. A means for quickly determining oxidation resistance has not been proposed yet.